Design of functionalized adsorbents for simultaneous removal of fluoride and arsenite from waters

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It was aimed to synthesize a modulator (benzoic acid (BA))-driven zirconium-fumaric acid (Zr-fum) metal-organic frameworks (MOF) and investigated in detail the adsorption mechanism of arsenic oxyanions (AsO43- and AsO33-) and their stability before and after the adsorption from water. The mechanism of AsO43- and AsO33- interaction on Zr-MOF was ligand-exchange and found to be the maximum uptake performance of AsO43- (1.159 mmol/g) and AsO33- (1.121 mmol/g) was obtained by the Langmuir adsorption isotherm. Likewise, it is also synthesized La-based MOFs with the linkers of benzoic acid (BA), 1,4-benzene dicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic acid (BTC). Interestingly, the ligand of BA approached La metal to form lanthanum methanoate (La(HCOO)3 instead of La-BA MOF through acid catalyst amide-hydrolysis mechanism, where, La-BDC and La-BTC as MOFs, confirmed by PXRD patterns. This is the first report to investigate the AsO43- adsorption and their dissolution behavior over La-BA, La-BDC and La-BTC in detail using the different spectroscopic methods. The maximum adsorption capacities of AsO43- obtained from the Langmuir isotherm model were found to be 2.623 mmol/g, 3.891 mmol/g and 0.280 mmol/g for La-BA, La-BDC and La-BTC, respectively. The value for La-BDC was recorded as one of the much superior, next to UiO-66, to the previously reported adsorbents for AsO43- till date. In addition, the zirconia nanoparticles (ZrO2) embedded graphene oxide dendrimer was prepared and utilized for removal of toxic AsO33- removal from water.